Pls advise Beijing - Chengde - Beijing - Datong - BJ

29/03 Am planning to take Beijing-Chengde (via train soft seat at 8.05am - 12.31pm). My question is where to take long distance bus from Chengde- BJ and cost how much and how many hours of journey it take as I need to catch BJ-Datong (via train soft bed at 11.42pm - 6.03am)? Pls advise. Thanks